Exhaust gas recirculation control system for an internal combustion engine

Abstract

An exhaust gas recirculation control system for an internal combustion engine comprises an exhaust gas recirculation control valve for controlling a recirculation rate for exhaust gas to be mixed with intake air which is supplied to the internal combustion engine, an oxygen sensor disposed in an intake air passage downstream of the control valve to detect the concentration of oxygen in the intake air, a control means which compares the oxygen concentration detected by the oxygen sensor with a desired oxygen concentration previously determined depending on operational conditions of the engine and controls the degree of opening of the exhaust gas recirculation control valve so as to cancel the deviation between the detected oxygen concentration and the desired oxygen concentration, a detecting means for detecting the exhaust gas recirculation rate being zero to supply a signal to the control means on the basis of the detection, and a correcting means for correcting the corresponding relation between the output of the oxygen sensor and the detected oxygen concentration on the basis of the output of the oxygen sensor when the exhaust gas recirculation rate is zero.

Dependencies are inferred from the claim text.